Nanoporous TiO₂ and WO₃ Films by Anodization of Titanium and Tungsten Substrates:  Influence of Process Variables on Morphology and Photoelectrochemical Response

Abstract

The photoelectrochemical response of nanoporous films, obtained by anodization of Ti and W substrates in a variety of corrosive media and at preselected voltages in the range from 10 to 60 V, was studied. The as-deposited films were subjected to thermal anneal and characterized by scanning electron microscopy and X-ray diffraction. Along with the anodization media developed by previous authors, the effect of poly(ethylene glycol) (PEG 400) or D-mannitol as a modifier to the NH4F electrolyte and glycerol addition to the oxalic acid electrolyte was studied for TiO2 and WO3, respectively. In general, intermediate anodization voltages and film growth times yielded excellent-quality photoelectrochemical response for both TiO2 and WO3 as assessed by linear-sweep photovoltammetry and photoaction spectra. The photooxidation of water and formate species was used as reaction probes to assess the photoresponse quality of the nanoporous oxide semiconductor films. In the presence of formate as an electron donor, the incident photon to electron conversion efficiency (IPCE) ranged from approximately 130% to approximately 200% for both TiO2 and WO3 depending on the film preparation protocol. The best photoactive films were obtained from poly(ethylene glycol) (PEG 400) containing NH4F for TiO2 and from aqueous NaF for WO3.

One-Dimensional Titanium Dioxide Nanomaterials: Nanotubes

“…Later work showed significantly improved control over length, diameter, ordering and composition by the use of pH mediation 116 , and particularly by the introduction of non-aqueous electrolytes 117,118,119 . It is noteworthy that fluoride based electrolytes were then also found to be an extremely versatile tool to grow ordered anodic oxide nanostructures on other metals, such as Hf, 120,121 Zr, [122][123][124][125][126][127] Fe, [128][129][130] , Nb, 131,132 V, 133 W, [134][135][136][137] Ta, [138][139][140][141][142] Co, 143 and even Si [144][145][146] .…”

Crystallite phase-controlled preparation, characterisation and photocatalytic properties of titanium dioxide nanoparticles

“…anodising of Ti) [20][21][22], solution combustion method [23][24][25], microemulsion [26,27], micelle and inverse micelle methods [28,29], ball milling [30], a flame by vapour phase [31], sonochemical reactions [32] and plasma evaporation [33,34]. It should be noted that as precursors of nanocrystalline oxide powders, however, inorganic compounds are more economical than alkoxides.…”

Characterization of Micron-Scale Nanotublar Super Dielectric Materials

“…As the experimental protocols were used, the specific procedures were adjusted according to the quality and dependability of the resulting anodic films. Ultimately, the procedures documented hereon closely resemble procedures outlined in existing literature [57], [65], but were altered in order to facilitate anodization in a simpler, less expensive laboratory environment.…”

“…Deionized water (DIW) was used to prepare all aqueous solutions. Nanoporous WO 3 films were created by anodizing 0.05 mm thick, 99.9% pure tungsten foil (Aldrich) substrates using a process similar to but unique from those described in the literature [57], [65]. ions from the pores and leave behind random pits [57].…”